Method for the production of hardmetal alloys



Patented July 7, 1942 METHOD FOR. THE PRODUCTION OF HARD METAL ALLOYSWalther Dawihl, Kohlhasenbruck, near Berlin, and Karl Schriiter,Berlin-Eichkamp, Germany, 'assignors to General Electric Company, acorporation of New York No Drawing. Application June 24, 1941, SerialNo. 399,530. In Germany June 10, 1940 3 Claims. (Cl. 106-43) Thetechnical experience which has been gathered as a result of themanufacture of hard metal alloys containing sintered tungsten carbideand titanium carbide has indicated that the main difiiculties in theproduction of high grade alloys having the most uniform constituencyresides in' the production and use of verypure titanium carbide.

In general, titanium carbide is obtained by the treatment of titaniumoxide with carbon; in

. contrast to the oxides of the elements of the sixth group of theperiodic system, a mixture of titanium oxide and carbon cannot becompletely transformed into titanium carbide. It has been found that atitanium carbide. obtained in this manner contains in addition to thetheoretical total carbon content, a few per cent of oxy en and a portionof uncombined carbon corresponding to the oxygen content, when suchtitanium carbide is further processed with tungsten carbide, possiblywith an addition of metals having a lower melting point, especiallymetals of the iron group (the auxiliary metal), there occur subsequenttransformations between the residual oxygen and the free carbon, andthese transformations have unfavorable chemical and physical effects onthe properties. of the hard metal alloys thus obtained, impairing theperformance of tools made from the alloy as well asproviding a. lack ofuniformity in the alloy and tools made therefrom.

According to the present invention, this difficulty in making sinteredhard metal alloys that contain tungsten carbide and titanium carbide, aswell as possibly an auxiliary metal, is avoided when one starts, notwith a titanium carbide produced directly from titanium oxide andcarbon, but when one produces titanium nitride by heating titanium oxidewith carbon in a nitrogen stream, and when this titanium nitride,together with the tungsten carbide and with the addition of the quantityof carbon calculated for convert-- ing the titanium nitride intotitanium carbide, are converted into a tungsten carbide-titanium carbidealloy. The technical advantages of this method lie, on the one hand, inthe fact that titanium nitride can be produced with a much lower oxygencontent than titanium carbide; on the other hand, when the titaniumnitride and the carbon are converted, in the presence of tungstencarbide, possible oxygen residues may be further eliminated.

Instead of the tungsten carbide it is also possible to use tungstenmetal, and then the required carbon addition is so calculated that thetungsten metal can be transformed, during the I process, into tungstencarbide.

The method may be carried out as follows: For instance, 100 parts oftitanium oxide are heated, together with 50 parts of lampblack, for

two hours, at a temperature of 1600 C. and in a nitrogen stream, and 15parts of the titanium nitride thus obtained are heated with 85 parts oftungsten carbide, with an addition of 3 parts of lampblack, for twohours, also up to 1600" C. but this time in a hydrogen stream. Underthese conditions, the titanium nitride is converted into titaniumcarbide, and nitrogen is released, while the 'tungsten'carbide isabsorbed by the titanium carbide produced, and that until saturation isattained, the solution being a solid solution. The tungstencarbide-titanium carbide alloy arrived at in this manner is thentriturated, and if necessary is processed with the addition of auxiliarymay be advisable sometimes to add to the mixmetals having a lowermelting point, by pressing followed by sintering, or by simultaneouspressingand sintering, until hard metal molded bodies are obtained. Iftungsten metal is employed instead of tungsten carbide, carbon must beadded to the mixture, in quantities which will correspond to thecomposition of the desired tungsten carbide. To facilitate thetransformations, it

tures to be heated, and that during the nitride production as well asduring the transformation.

of the nitride into carbide,'ajpart of the metals having a lower meltingpoint, for instance 1 to 2 per cent cobalt. One may also subject themixture of titanium nitride and carbon to a preheating process, and addthe tungsten carbide subsequently.

The hard metal alloys obtained in this manner have a very high cuttingcapacity and are particularly uniform in their composition.

What we claim as new and'desire to secure by Letters Patent of theUnited States, is: 1. The method for producing a solid solutionconsisting of tungsten carbide-and titanium carbide which comprisesheating titanium oxide in an atmosphere of nitrogen and in the presenceof carbonto thereby obtain titanium nitride, heating the titaniumnitride thus obtained with tungsten carbide and carbon in a reducingatmosphere at a temperature sufiiciently high to produce a solidsolution of tungsten carbide and titanium carbide.

' 2.- The method for producing a solid solution of tungsten carbide andtitanium carbide which comprises heating about 100 parts of titaniumoxide withabout 50 parts of pulverized carbon comprises heating about 15parts of titanium nitride with about 85 parts tungsten carbide and about3 parts pulverized carbon in an atmosphere of hydrogen and at atemperature of about 1600 C. and for a period or time long enough toform a solid solution of tungsten carbide and titanium carbide.

WAL'I'HER DAWIHL. KARL scrmo'mn.

